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Prostate cancer is the most diagnosed noncutaneous cancer and ranks as the second leading cause of cancer-related deaths in American males. Metastasis is the primary cause of prostate cancer mortality. Survival rate is only 28% for metastatic patients, but is nearly 100% for patients with localized prostate cancers. Molecular mechanisms that underlie this malignancy remain obscure, and this study investigated the role of SPARC/osteonectin, cwcv, and kazal-like domain proteoglycan 1 (SPOCK1) in prostate cancer progression. Initially, we found that SPOCK1 expression was significantly higher in prostate cancer tissues relative to noncancerous tissues. In particular, SPOCK1 expression was also markedly high in metastatic tissues compared with nonmetastatic cancerous tissues. SPOCK1 expression knockdown by specific short hairpin RNA in PC3 cells was significantly inhibited, whereas SPOCK1 overexpression in RWPE-1 cells promoted cell viability, colony formation in vitro, and tumor growth in vivo. Moreover, the SPOCK1 knockdown in PC3 cells was associated with cell cycle arrest in G0/G1 phase, while the SPOCK1 overexpression in RWPE-1 cells induced cell cycle arrest in S phase. The SPOCK1 knockdown in PC3 cells even increased cell apoptosis. SPOCK1 modulation was also observed to affect cancerous cell proliferation and apoptotic processes in the mouse model of prostate cancer. Additionally, the SPOCK1 knockdown decreased, whereas the SPOCK1 overexpression increased cell migration and invasion abilities in vitro. Injection of SPOCK1-depleted PC3 cells significantly decreased metastatic nodules in mouse lungs. These findings suggest that SPOCK1 is a critical mediator of tumor growth and metastasis in prostate cancer.

Micro (mi)RNAs are a group of small non-coding RNA molecules that have been demonstrated to regulate the expression of genes involved in tumorigenesis. The relevance of microRNAs in the development, progression and prognosis of prostate cancer is not fully understood. miR-155 has been implicated in the induction of breast, lung and liver cancer, but its role in prostate cancer has not been investigated. In the present study, the biological function of miR-155 was investigated in prostate cancer for the first time, to the best of our knowledge. It was demonstrated that the expression of miR-155 was upregulated in prostate cancer tissues and cell lines as determined by quantitative reverse transcription-polymerase chain reaction. Furthermore, overexpression of miR-155 promoted cell proliferation, as indicated by MTT assay. Flow cytometric analysis demonstrated that inhibition of miR-155 induced cell cycle arrest and promoted apoptosis in prostate cancer cells. In addition, western blot analysis indicated that annexin (ANX)7 was significantly downregulated in prostate cancer tissues and cells. A luciferase reporter assay indicated that ANX7 was a target of miR-155, which suggested that miRNA-155 promoted the proliferation of prostate cancer cells by regulating ANX7 expression levels.

Aims: To investigate global proteomic changes induced in CD44+CD24- stem cells isolated from the prostate cancer cell lines, LNCaP and DU145, post prolonged TGF-β treatment in order to understand underlying mechanisms that promote stemness in prostate cancer cells., Methods: CD44+CD133+α2β1Integrin+CD24- population was isolated from mock or TGF-β treated (7 days) prostate cancer cell line, LNCaP, through fluorescent activated cell sorting. Cell lysates were obtained from the ±TGF-β cell population and proteomics profiling (MS/MS) was performed by mass spectrometry. Relative enrichment or depletion in the CD44+CD24-population post-TGF-β treatment was determined relative to mock-treated CD44+CD24- cells post normalization to GAPDH expression levels. RESULTS obtained from MS/MS were validated using immunoblotting. Functional validation of one putative regulator was performed using gain-of-function strategy to investigate its role in rendering stemness in LNCaP and DU145 cells in vitro and in promoting tumorigenicity in vivo., Results: TGF-β treatment caused significant enrichment of CD44+CD24- population in LNCaP cells (22.35 ± 0.94% in mock treated vs 95.23 ± 2.34% in TGF-β treated cells; P < 0.01), which were also positive for CD133 and α2β1Integrin. Mass spectrometry analysis of the enriched cell population revealed that sixty-three proteins were either up- or down-regulated greater than five folds, out of which the poly r(C) binding protein (PCBP)-1 was the most down-regulated (9.31 ± 0.05 folds). Ectopic overexpression of PCBP1 in LNCaP and DU145 cells not only attenuated enrichment of CD44+CD133+CD24- population in these cells following TGF-β treatment, but also significantly decreased tumorigenicity of the stem cell subset, as assessed by in vitro soft agar colony formation and in vivo xenograft assays., Conclusion: Our proteomic profiling and subsequent validation indicate that PCBP1 is central to CSCs enrichment and functionality in prostate cancer., (© 2015 S. Karger AG, Basel.)